For decades scientists have hunted for the most elusive particles that they think
exists almost everywhere... Dark Matter.
Every time they looked they came up empty handed, except for one experiment. The
DAMA/LIBRA experiment which has continuously observed a significant signal for about 20 years.
Up until recently no one has attempted to replicate their experiment. Now two independent
teams both confirmed that they cannot reproduce the results. Let's dive in and find out more.
The term dark matter was first coined back in 1884 when Lord Kelvin estimated the number of Dark
Bodies in the Milky Way from observed velocities of stars orbiting the centre of the galaxy. From
this he estimated the mass of the galaxy, which he determined was different from the mass of visible
stars. He concluded “many of our stars, perhaps a great majority of them, maybe dark bodies.
In 1906 Henri Poincare when referring to Lord Kelvin’s work first used the term Dark Matter.
When we observe the effects of gravity on large objects which rotate around a central axis
there is a ratio that holds true no matter what the size of the body. This amazing ratio was first
discovered by Johannes Kepler in the 17th century. He was a german astronomer, mathematician and
astrologer. He was an assistant to Tycho Brahe. Who meticulously catalogued the position of the
stars and planets over many years. Tycho was a firm believer in the notion that the earth was
at the centre of the universe and was busy trying to update Ptolemy's model of the solar system.
Kepler had very different ideas about the structure of the universe and saw something
in the data that Tycho had collected over many many years. He was, over a period of many years,
without the aid of calculators or log tables able to construct the Kepler laws of planetary motion.
All the more remarkable is that his 3rd law is basically Newton's law of gravitation
which would not be penned for at least another 100 years. In this law it states that the square of
the time period of rotation of a planetary body is related directly to the cube of the radius.
In other words, it has nothing to do with it’s mass, the further out a body is the longer it
takes to orbit around the centre. This simple statement holds exactly for our solar system.
If the mass of the central object increased more gravity would be generated and the objects would
rotate faster. If an object rotated faster than it’s orbit would allow
it would move further out, either reaching orbit further away or leaving the system
altogether. Also if the object was slowed down it would spiral inwards, increasing its
speed until it either reached another more stable orbit or it collided with the sun.
As our telescopes improved and we were able to observe the rotation rate of galaxies
something curious started to be observed. The galaxies were rotating with such speed that the
gravity generated by the observable matter could not possibly hold it together. It should have
flown apart eons ago. When they observed spiral galaxies they realised that the arms of the spiral
should have long disappeared as the rotation rate on the outside should have been much slower.
In fact what they saw was the whole galaxy was rotating at a similar speed,
much more like a record or merry go round.
In order to solve this problem they determined that there must be hidden dark matter
spread through the galaxy causing extra mass and hence gravitation effect
to account for this increased rotation on the outer edge. The problem was that this matter
could not interact with normal matter in any other way than gravity otherwise we would have detected
it. This makes detecting it almost impossible. We are talking about a substance that allows
light to pass right through it, normal matter too will pass right through it.
The only effect you will see are the perturbation caused by gravity.
Cosmic background radiation should have developed into a very uniform pattern. It did not and this
implies that something must have caused the matter to clump together in this strange pattern. So
they invoke dark matter but don’t explain how dark matter clumped there in the first place!
So when they refer to the fact that there is good astronomical data to support Dark matter
they are simply referring to the fact that there are problems with their model
in a variety of different places that could be fixed using Dark Matter.
And their models with Dark to some extent do predict the correct rotation speed for example
but the same could be said of Ptolemy's epicycles which with ever more complex epicycles was able
to a large extent predict the correct positions of the planets despite it being the wrong model.
So finding evidence of Dark Matter is a big deal and DAMA/LIBRA claimed back in 2018 that they had
found physical evidence of dark matter in the form of flashes of light in sodium iodide crystals. The
researchers believed the flashes were evidence of dark matter colliding with atoms in the crystals.
They found a that these flashes of light increased in number every June and lessened every December.
This they suggested was because of the way Earth moved through Dark Matter in the Milky Way.
In the most recent attempt researchers in Korea tried to replicate the findings.
When they observed the crystals over a prolonged period of time they were not able to observe any
flashes in their crystals, striking another blow to the results of the DAMA/LIBRA.
Yet still the funding and the hunt goes on.
To make the whole thing even more surreal a new theory now suggest that dark matter
can create new Dark Matter from regular matter. Yep that's right, the invisible
undetectable dark matter which only interact with regular matter through gravity can now sometimes
convert regular matter to dark matter. One of the reasons they feel this might be useful is that it
would simply the explanation of how all the dark matter came into existence in the first place.
In this theory you would only require some point dark matter particles which would then begin
making new dark matter particles out of regular particles. Sort of like a Dark Matter plague
spreading across the universe, maybe they have been reading too many science fiction novels?
So surely that would mean that eventually the universe would be all be converted
into Dark Matter... right? Expansion to the rescue, yes the researchers believe that our
universe was saved as it was expanding fast to slow the conversion process,
leaving us with just the amount that is believed to exist today... how incredibly convenient!
Furthermore they claim that their theory can be tested as they claim there should
be an observable fingerprint left behind in the cosmic background radiation...
all that needs to be done now is find it...
One fix after another and yet they still can't find Dark Matter
but keep searching and coming up with new fixes!
And on that note I will leave you to cogitate.